Source : Webster's Revised Unabridged Dictionary (1913)

Maturely \Ma*ture"ly\, adv.
   1. In a mature manner; with ripeness; completely.

   2. With caution; deliberately. --Dryden.

   3. Early; soon. [A Latinism, little used] --Bentley.

Source : WordNet®

maturely
     adv : in a mature manner; "she acts very maturely for her age"
           [ant: {immaturely}]